public class J2103 {
    public static int find(int[] arr){
        int m = arr.length;
        int flage = 0;
       for(int i = 0; i < m; i++){
           flage ^= arr[i];
       }
       return flage;
    }

    public static void main(String[] args) {
        int[] nums = new int[]{2,5,10,9,8,5,2,8,9};
        System.out.println(find(nums));
    }
}
